I have a workshop, with a single layer, no cavity, block wall and
dubious foundations. It was built some uncertain time ago ('50s?
'20s?) by a chap with scant regard for planning or building
regulations. The rendering is cracked, and some of these cracks go
right through, hence are leaky (no cavity!)

http://codesmiths.com/dingbat/lj/20080718/FXCD0051%20(Medium).JPG

So now I'm looking at possible solutions to stop any movement here,
before I start papering over the cracks and trying to get the render
waterproof. I'm wondering about a stainless twisted-bar kit like this
- any experience of advice with them?

http://www.twistfix.co.uk/2005_shop/product.asp?
productID=267&categoryID=170
(Toolstation & Screwfix have similar kits, for nearly twice as much)

My worst cracks are a couple of horizontals and a couple of verticals,
both of which appear to be settlement cracks owing to inadequate
foundation. It's not so bad I'm having to tie the walls back on, but I
would like to stop movement enough to keep the render watertight. Are
these helical bars usable in arbitrary chases through the blockwork,
or are they only for mortar joints between bricks?

All suggestions welcome!

Andy Dingley wrote:

So now I'm looking at possible solutions to stop any movement here,
before I start papering over the cracks and trying to get the render
waterproof. I'm wondering about a stainless twisted-bar kit like this
- any experience of advice with them?

http://www.twistfix.co.uk/2005_shop/product.asp?
productID=267&categoryID=170
(Toolstation & Screwfix have similar kits, for nearly twice as much)

I have seen them used (Helibars I think the trade name was) and they
were very effective - they used about three or four of them to tie a 9"
solid wall, with a floor to ceiling crack, back onto the back of a large
Victorian semi.

My worst cracks are a couple of horizontals and a couple of verticals,
both of which appear to be settlement cracks owing to inadequate
foundation. It's not so bad I'm having to tie the walls back on, but I
would like to stop movement enough to keep the render watertight. Are
these helical bars usable in arbitrary chases through the blockwork,
or are they only for mortar joints between bricks?

They can certainly be applied after the fact. Cut a slot with an angle
grinder and bond them in place with the appropriate gloop. The guide on
that site you linked seems to include a decent description:

http://www.twistfix.co.uk/upload/viewer.asp?id=117

If you want to make sure the render can't crack afterwards, hack it off
in the area of the repair, and then fix some expanded stainless lath
over the area, fixing well with screws and plugs through penny washers
on a random-ish 150mm fixing pattern. Then render over.

--
Cheers,

John.

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On 17 Feb, 14:23, John Rumm wrote:

They can certainly be applied after the fact.

Thanks. Any thoughts on numbers or orientation? I'm assuming right
angles to the crack and spacing as per their note, but that's for
horizontal ties and my two biggies are horizontal cracks.


If you want to make sure the render can't crack afterwards,

On the whole, I think I like the idea of using the render as a
"canary" in case of further movement. It's not so high that I can't re-
render for far less effort than I'd be facing if I did see future
movement.

Andy Dingley wrote:
On 17 Feb, 14:23, John Rumm wrote:

They can certainly be applied after the fact.

Thanks. Any thoughts on numbers or orientation? I'm assuming right
angles to the crack and spacing as per their note, but that's for
horizontal ties and my two biggies are horizontal cracks.

If you are rendering over, there is probably no harm in just going
perpendicular to the crack regardless of orientation. Obviously with
visible brickwork, a bar orientation of horizontal is preferred for any
crack since it can be hidden completely in a mortar joint.

So you would need vertical bars for the horizontal cracks, and
horizontal bars for the vertical ones ;-) However it strikes me that
settlement alone does not usually give horizontal cracks, unless there
are also some vertical or diagonal ones near by. In which case you can
bar fix the vertical/diagonal ones and then just patch (or resin fill)
the horizontal ones.

If you want to make sure the render can't crack afterwards,

On the whole, I think I like the idea of using the render as a
"canary" in case of further movement. It's not so high that I can't re-
render for far less effort than I'd be facing if I did see future
movement.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

Andy Dingley wrote:
On 17 Feb, 14:23, John Rumm wrote:

They can certainly be applied after the fact.

Thanks. Any thoughts on numbers or orientation? I'm assuming right
angles to the crack and spacing as per their note, but that's for
horizontal ties and my two biggies are horizontal cracks.


If you want to make sure the render can't crack afterwards,

On the whole, I think I like the idea of using the render as a
"canary" in case of further movement. It's not so high that I can't re-
render for far less effort than I'd be facing if I did see future
movement.


You can bond bars in to restore the integrity of the wall, but really
its not going to stop the building moving in future. The wall will
simply crack somewhere else. Re helibars, ss threaded rod is way
cheaper.

A much simpler way to reintegrate the wall would be to inject epoxy
into the cracks.


NT

On 17 Feb, 15:32, John Rumm wrote:

However it strikes me that
settlement alone does not usually give horizontal cracks,

No, I'm sure it doesn't. But this isn't the "usual" set of
foundations!

There are two gable-ended buildings, end-on-end and one narrower than
the other. The end of the narrow one is open, spanned by a steel
girder about 15' wide. As far as I can see, the root of the problem is
that the inner corner is carrying much of the weight of the large
gable and also one end of the girder. It gets little support from the
wall as there's a door in it, although there is a little buttressing
to thicken it, I suspect that the foundations here are inadequate for
the load and have settled downwards. The two horizontal cracks (photo)
are above this in the large gable and also running from the bottom
left corner of the window in the white-painted wall. There's also the
vertical crack above this pillar. So the whole pillar seems to have
moved downwards by 1/2" - 1" leaving part of the gable above it
hanging as an arch(?).

http://codesmiths.com/dingbat/lj/200...20(Medium).JPG

On 17 Feb, 16:55, wrote:

Re helibars, ss threaded rod is way cheaper.

Helibar are £5 each, which is cheaper than threaded stainless rod,
unless you go down to 8mm. I'd also be concerned about grip on the
much smaller thread.


A much simpler way to reintegrate the wall would be to inject epoxy
into the cracks.

That's going to put the faces of the crack into tension though, so
won't that simply peel the epoxy off the crack? The point of the bars
is to couple the forces in along a long shear line.

In message
,
Andy Dingley writes
On 17 Feb, 16:55, wrote:

Re helibars, ss threaded rod is way cheaper.

Helibar are £5 each, which is cheaper than threaded stainless rod,
unless you go down to 8mm. I'd also be concerned about grip on the
much smaller thread.

I've just bought a metre of m12 stainless studding for a fiver.


A much simpler way to reintegrate the wall would be to inject epoxy
into the cracks.

That's going to put the faces of the crack into tension though, so
won't that simply peel the epoxy off the crack? The point of the bars
is to couple the forces in along a long shear line.

Have you totally rejected underpinning?

regards

--
Tim Lamb

Andy Dingley wrote:
On 17 Feb, 16:55, wrote:

Re helibars, ss threaded rod is way cheaper.

Helibar are £5 each, which is cheaper than threaded stainless rod,
unless you go down to 8mm. I'd also be concerned about grip on the
much smaller thread.

I was thinking of smaller than that, M6. The rod isnt going to carry
structural weight, it just keeps the wall sections in line so they can
bear down on each other.


A much simpler way to reintegrate the wall would be to inject epoxy
into the cracks.

That's going to put the faces of the crack into tension though, so
won't that simply peel the epoxy off the crack? The point of the bars
is to couple the forces in along a long shear line.

Why do you think that would be in tension? The concrete is stationary,
at least for now. No matter how you bond the bits back, the wall will
inevitably crack if/when it moves again, whether it cracks at the same
place or elsewhere - and actually its better if it cracks at the same
place, a wall cracked into 4 pieces is a lot better than a wall in 8.

Any attempt to stop future cracking just isnt going to happen, unless
the root problem is addressed, or the wall replaced with a more
flexible type. So unless the place is getting underpinned etc, what's
best is a repair that allows a break in the same place in future if it
moves again. 20 or 30 notes, an hour or 2 with a ladder and you're
done. And with that level of input its no biggie to re-fix it in
future.


NT

On 17 Feb, 19:05, Tim Lamb wrote:

Have you totally rejected underpinning?

Haven't considered it in detail yet. I'm capable of stitching the
cracks myself, but probably not capable of doing this underpinning.
There are also questions of needing to clear a lot of access to even
start looking at it and yet wanting a "quick fix" to water ingress
now, even if it's wasted in the future. I can actually see myself
doing it with aluminium tape, just to waterproof it temporarily.

There's also a couple of cubic yards of concrete path to replace with
grass outside, and some of that's in the corner where we'd be doing
the underpinning. At least some of that ought to go before we get
started seriously.

Oh, and there's a waterpipe running through the whole mess. Probably
in lead. No-one knows quite where. That also suggests there's drainage
somewhere nearby, but I can't find that either.

wrote in message
...

You can bond bars in to restore the integrity of the wall, but really
its not going to stop the building moving in future. The wall will
simply crack somewhere else.

Settlement or subsidence?
Settlement being a one time thing shortly after building.
But is there really any such thing as settlement?
I have no special knowledge but guess that there only subsidence.
Subsidence being an ongoing thing. e.g. the leaning tower at Pisa.

My anecdote refers to the subsidence of an extension to my block built
garage. The subsidence was under the far end wall causing the whole
extention to tip away from the original structure leaving a tapering
vertical crack of up to an inch at roof level on both sides. The crack had
occurred at the join of the original and extension. On one side there was a
door opening and on the other a window opening with only a few courses of
block work, so there was virtually no keying in of the extension blockwork
to the original structure.

I tried to repair/solve the problem by replacing the broken blocks and
reducing the opening on the side with the window. It did not crack there
again, but after six months a new crack from floor to roof appeared a couple
of meters further along the garage wall, breaking the concrete blocks in
half at that location.

The subsidence could not be restrained by attempting to support the
subsiding part by keying it into the existing sound structure, the weight of
the extension was just too great for the strength of concrete blocks.
Demolition and rebuild of the garage with sounder foundations would appear
to be the only effective solution.

My garage is quite different to your building, but the experience would seem
to agree with meow222, that the cracks may simply transfere to a weaker
point somewhere else.
Note that I am not a structural engineer or a builder.

On 18 Feb, 11:46, "Roger R" wrote:

Settlement or subsidence?
Settlement being a one time thing shortly after building.

Settlement, very likely, as the ground conditions aren't conducive to
subsidence (major geosurveying works on exactly that, within 50 yards)
and the build quality of the whole edifice is best described as "****
poor" with far from adequate foundations.


My anecdote refers to the subsidence of an extension to my block built
garage. *The subsidence was under the far end wall causing the whole
extention to tip away from the original structure leaving a tapering
vertical crack of up to an inch at roof level on both sides. *

I've got one of those too 8-) That's on the other side, a different
era of building, and I'm planning a 8' tie-rod to deal with it.


My garage is quite different to your building, but the experience would seem
to agree with meow222, that the cracks may simply transfere to a weaker
point somewhere else.

In this case there isn't a "weaker point", as I'm talking about a
pillar in an internal corner which is the junction of a 15' girder
span, a window (white painted in the photo) and a doorway. It's
already the _only_ point carrying the load - anything else nearby is
an open space. There's a lot of load concentrated in this one spot
with not much adjacent to it and that seems to have compressed the
inadequate foundations.

Underpinning is a possibility. Jack under the girder, then go
underneath it from the existing doorway. Expensive, and it probably
involves external contractors.

Simplest is to to assume (nay, to hope) that the existing foundation
has compressed as much as it's going to and just deal with the crack.
Works fine, as far as your assumption holds.

What I'm most likely to do is to deal with the cracks, then brick up
the unused doorway and attempt to transfer some load from the gable
away from the pillar and into this new ex-doorway masonry, on an
adequate foundation.

In message
,
Andy Dingley writes
On 17 Feb, 19:05, Tim Lamb wrote:

Have you totally rejected underpinning?

Haven't considered it in detail yet. I'm capable of stitching the
cracks myself, but probably not capable of doing this underpinning.
There are also questions of needing to clear a lot of access to even
start looking at it and yet wanting a "quick fix" to water ingress
now, even if it's wasted in the future. I can actually see myself
doing it with aluminium tape, just to waterproof it temporarily.

I'm no expert but... a chap who does odd bits of groundwork for me
specialises in underpinning work for the insurance companies. We were
discussing how to go about creating concrete pads to support a steel
portal frame inside my timber barn. The architects have drawn a fancy
Acrow propping arrangement to take the load off the foundations. He said
this is unnecessary as most of his work is done by simply undermining
the foundations in 1m blocks and back filling with poured concrete.
Apparently the jobs sometimes require rammed dry mix for the 2" or so
actually in contact with the original foundation. Cue Huge:-)

There's also a couple of cubic yards of concrete path to replace with
grass outside, and some of that's in the corner where we'd be doing
the underpinning. At least some of that ought to go before we get
started seriously.

Better the deed, better the day!

Oh, and there's a waterpipe running through the whole mess. Probably
in lead. No-one knows quite where. That also suggests there's drainage
somewhere nearby, but I can't find that either.

Just think how much more easily you will rest not supping leaded water.

regards

--
Tim Lamb

Simplest is to to assume (nay, to hope) that the existing foundation
has compressed as much as it's going to and just deal with the crack.
Works fine, as far as your assumption holds.


there is some way of cementing in a scale
which you can measure in a year to see how much movement there is...
let me know when you find it out
cos ive got a few cracks too...
(in my house that is)

[g]

On 18 Feb, 22:35, "george (dicegeorge)" wrote:

there is some way of cementing in a scale
which you can measure in a year to see how much movement there is...

Had a couple of those in my first house - a terrace on a steep hill.
You could see one of them move out 1/4", then move back later in the
year.

On 18 Feb, 18:32, Tim Lamb wrote:

this is unnecessary as most of his work is done by simply undermining
the foundations in 1m blocks and back filling with poured concrete.

One of our neighbours used the same technique on his barn -- Or "the
rubble pile" as it's now known, Plain poured concrete has a ****ing
terrible reputation for underpinning, as it's difficult to get
adequate compaction with it and then you get the same old settlement
problem.

If I did underpin this, then I'd have to prop the girder. If I prop
the girder, the rest is easy (working the hole from outside). Still a
big job, and a Summer job though.

Tim Lamb wrote:

I'm no expert but... a chap who does odd bits of groundwork for me
specialises in underpinning work for the insurance companies. We were
discussing how to go about creating concrete pads to support a steel
portal frame inside my timber barn. The architects have drawn a fancy
Acrow propping arrangement to take the load off the foundations. He said
this is unnecessary as most of his work is done by simply undermining
the foundations in 1m blocks and back filling with poured concrete.
Apparently the jobs sometimes require rammed dry mix for the 2" or so
actually in contact with the original foundation. Cue Huge:-)

A mate of min used to do similar stuff - often with angered piles to pin
the resulting concrete beams in place. Apparently they would use the
same undermining hit and miss technique, then they would insert
disposable jacks to prop up the bits they had undermined. Then undermine
the rest. Make up some rebar cage forms ready for the concrete pour (if
piles were involved then these would be done first and their tops and
rebar would be integrated into the beams). Then pour the concrete. Once
that had gone off, slate or dry pack could be used to take up any
shrinkage (plus the jacks would still be in place obviously).

--
Cheers,

John.

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\================================================= ================/

george (dicegeorge) wrote:


Simplest is to to assume (nay, to hope) that the existing foundation
has compressed as much as it's going to and just deal with the crack.
Works fine, as far as your assumption holds.


there is some way of cementing in a scale
which you can measure in a year to see how much movement there is...
let me know when you find it out
cos ive got a few cracks too...

Quite often done with three measuring points either side and above the
crack (most are slightly diagonal). These are epoxied into drilled
wholes. Just take readings between them with callipers.

--
Cheers,

John.

/================================================== ===============\
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| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

In message
,
Andy Dingley writes
On 18 Feb, 18:32, Tim Lamb wrote:

this is unnecessary as most of his work is done by simply undermining
the foundations in 1m blocks and back filling with poured concrete.

One of our neighbours used the same technique on his barn -- Or "the
rubble pile" as it's now known, Plain poured concrete has a ****ing
terrible reputation for underpinning, as it's difficult to get
adequate compaction with it and then you get the same old settlement
problem.

Oh! They have an air driven vibrating poker to get rid of voids but I
guess, if the subsoil gives inadequate support, things will still move.
1.2m down here and you are in very firm stuff.

If I did underpin this, then I'd have to prop the girder. If I prop
the girder, the rest is easy (working the hole from outside). Still a
big job, and a Summer job though.

Why not offer training opportunities for ex-city types? Re-tune flabby
muscles etc.

regards

--
Tim Lamb

On 19 Feb, 08:50, Tim Lamb wrote:

Why not offer training opportunities for ex-city types? Re-tune flabby
muscles etc.

What do you think the timber framing training workshop is for! 8-)

On 19 Feb, 01:58, John Rumm wrote:

A mate of min used to do similar stuff - often with angered piles

He needs one of those air suspension seats when he's driving the
digger...

In message
,
Andy Dingley writes
On 19 Feb, 08:50, Tim Lamb wrote:

Why not offer training opportunities for ex-city types? Re-tune flabby
muscles etc.

What do you think the timber framing training workshop is for! 8-)

Ah! I've got one of those for my own use. You need big doors if you are
going to assemble in comfort.

regards

--
Tim Lamb

In message , Huge
writes
On 2009-02-18, Tim Lamb wrote:
In message

Apparently the jobs sometimes require rammed dry mix for the 2" or so
actually in contact with the original foundation. Cue Huge:-)

Huh? )

I didn't understand it either. Something like the original foundation is
not in direct contact with the underpin block but rests on a layer of
hard rammed sand/cement mix. I thought you might be able to explain the
reasoning:-)

regards


--
Tim Lamb

On Sat, 21 Feb 2009 18:43:49 +0000 Tim Lamb wrote :
I didn't understand it either. Something like the original
foundation is not in direct contact with the underpin block but
rests on a layer of hard rammed sand/cement mix. I thought you
might be able to explain the reasoning:-)

Yes, you need to be sure that the existing foundation is fully
supported on the new base. If you just filled the hole up in one go
there would be no way of ensuring compaction at the back and the new
concrete would shrink a little anyway. So, as described about, the
top of the new base should be about 50mm below the underside of the
existing footing and once it is hard the gap is filled in with 'dry
pack', a mix of cement and sharp sand 1:1-2 with just enough water
to hold it together. This is pushed into the gap and rammed tight
with something like a hammer and piece of 4x2 so that the gap is
fully filled.

--
Tony Bryer, 'Software to build on' from Greentram
www.superbeam.co.uk www.superbeam.com www.greentram.com

In message , Tony Bryer
writes
On Sat, 21 Feb 2009 18:43:49 +0000 Tim Lamb wrote :
I didn't understand it either. Something like the original
foundation is not in direct contact with the underpin block but
rests on a layer of hard rammed sand/cement mix. I thought you
might be able to explain the reasoning:-)

Yes, you need to be sure that the existing foundation is fully
supported on the new base. If you just filled the hole up in one go
there would be no way of ensuring compaction at the back and the new
concrete would shrink a little anyway. So, as described about, the
top of the new base should be about 50mm below the underside of the
existing footing and once it is hard the gap is filled in with 'dry
pack', a mix of cement and sharp sand 1:1-2 with just enough water
to hold it together. This is pushed into the gap and rammed tight
with something like a hammer and piece of 4x2 so that the gap is
fully filled.

Right.

Not the easiest job I guess, as you have just filled up the hole you
were standing in and can't dig the next until you have properly
supported the first bit:-)

regards


--
Tim Lamb

On 22 Feb, 08:43, Tim Lamb wrote:

Not the easiest job I guess, as you have just filled up the hole you
were standing in and can't dig the next until you have properly
supported the first bit:-)

I suggest reading a copy of "The Winchester Diver" before starting,
then not complaining!

Andy Dingley wrote:
On 22 Feb, 08:43, Tim Lamb wrote:

Not the easiest job I guess, as you have just filled up the hole you
were standing in and can't dig the next until you have properly
supported the first bit:-)

I suggest reading a copy of "The Winchester Diver" before starting,
then not complaining!

Agreed! Then he died of flu!

(Mrs Pierce, in this story about the diver, is my mother.
http://www.thehds.com/events/walker.html )

--
Rod

Hypothyroidism is a seriously debilitating condition with an insidious
onset.
Although common it frequently goes undiagnosed.
www.thyromind.info www.thyroiduk.org www.altsupportthyroid.org

In message
,
Andy Dingley writes
On 22 Feb, 08:43, Tim Lamb wrote:

Not the easiest job I guess, as you have just filled up the hole you
were standing in and can't dig the next until you have properly
supported the first bit:-)

I suggest reading a copy of "The Winchester Diver" before starting,
then not complaining!

I vaguely knew about that. Build not your cathedrals on a bog?

regards

--
Tim Lamb